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Thread: Tascam 388 Control board problem

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    Tascam 388 Control board problem

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    Hello, I'm a newbie to posting here and I was just wondering if anyone can give some tech advice...

    I have recently been fixing up a Tascam 388, the machine now seems to be all working after fixing several problems. As far as I can tell all the transport now functions, and it passes audio on all channels, meters work etc. Though I have not yet tested every single audio routing.

    Anyway... my current problem is a large thermal resistor on the control pcb (2w 47k) R405 which is getting super hot right away when turning the machine on. I know somethings not right there and is drawing too much current?

    When I first got the machine there were burned flux/heated marks from this resistor around the area and on the inside casing of the machine it's self, the old resistor seemed fine when I tested it, but replaced it anyway. There is a cap close to it that looks to of had some heat now also... visually everything else looks ok - I did recapped all the board and hoped this would get rid of the problem, but has not. I'm thinking it must be a short somewhere on the board or a power supply problem?...

    When testing voltages on the mother board (2) at power supply pcb pins, I'm getting high readings on two of the feeds on both AC and DC. The other one is correct and what I would expect.
    Would this be related to my control board resistor problem??
    Is something drawing too much power? or not enough power to get the higher volt readings? or is this a different problem altogether?

    I could be testing it wrong but have double check a few times now? it's strange as everything seems to be working fine regarding the transport etc?

    Has anyone had a similar problem and how did they resolved it? or If anyone has any ideas of what I should look at/check next regarding this it would be a great help.

    I maybe missing something really simple but thought I would ask here first before I start taking it apart again.
    Thanks in advance
    Robin

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    Typically if a fuse resistor or Metal Oxide resistor heats that fast there is excessive current and so there is a short down the line. This can either be found using a DVM on diode test or Ohms. Once the low resistance is found then that will fix the resistor heating problem. Too many people go into these things thinking they know how to fix them then we come upon a post where they can not even run down a simple short circuit and so it is time to move up to the next level and do what a real Technician would do and fix the deck.
    There are fewer and fewer people fixing these now- I can count on one hand those left some are retiring.

    IF the short is a dynamic type then put in a higher wattage resistor of a greater value and find the part that when disconnected allow the voltage to go up to the normal level- this will be a task to use divide and conquer method. Bad parts do not always hold up their hands to tell you where they are.
    Best regards,
    Skywave Tape Deck Repair, Chicago area

  3. #3
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    Thanks for the comment. The issue had been resolved in the below thread.
    Tascam 388 extremely hot control pcb resistor...

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